JPH05104678A - Pneumatic radial tire having improved durability at belt part - Google Patents

Abstract

PURPOSE:To prevent the end part of belt layer from separating and uniformize the physical properties such as modulus and the like of a tire by a method wherein rubber composition, which is prepared by compounding the partial condensation product, cresol resin, sulfur and the cobalt salt of organic acid with stock rubber, is employed so as to arrange at the ends between belt layers. CONSTITUTION:The belt pant concerned has at least two belt layers 4u and 4d made of aromatic polyamide fiber cord or steel cord and edge tapes 5 arranged between the ends of these two belt layers 4u and 4d. As the coating rubber of the belt layers 4u and 4d and edge tapes 5, rubber prepared by compounding 1.0-5 pts.wt. of the partial condensation product of hexamethylol melamine pentamethyl ether, 0.5-pts.wt. of cresol resin, 4-7 pts.wt. of sulfur and 0.1 0.8 pts.wt. in term of cobalt element of organic cobalt salt with 100 pts.wt. of stock rubber, is used. Thus, the separation of the ends of the belt layers is prevented from generating and the durability of belt is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having two belt layers each having an aromatic polyamide fiber cord or a steel cord as a reinforcing fiber cord.

[0002]

2. Description of the Related Art The same kind of rubber as the coat rubber of the belt layer is arranged in a tape shape on the edge portion of the belt layer of a radial tire.
It is well known that the durability of the belt edge portion (hereinafter referred to as edge tape) is improved. It is necessary for the coat rubber to have high hardness in order to improve the durability of the belt portion, and the adhesion between the coat rubber and the cord is achieved by using a resorcin resin, a melamine derivative and silica in combination with a cobalt salt as an adhesion promoter. It is well known (Japanese Patent Publication No. 63-4582).

However, in the above formulation, the breaking property of the coated rubber itself is deteriorated by the thermosetting reaction, and there is a problem that the separation property of the belt edge part is deteriorated when it is used as an edge tape. We have
The present invention has been found out by intensively studying a radial tire using one type of the same rubber composition as the belt coat rubber and the edge tape rubber.

[0004]

The object of the present invention is to apply a rubber composition having the same excellent adhesiveness and water resistance to aramid fiber cords (aromatic polyamide fiber cords) and steel cords as coat rubbers for both. Another object of the present invention is to provide a pneumatic radial tire (hereinafter simply referred to as a tire) which is also used as an edge tape to prevent the occurrence of separation at the end portion of the belt layer and to improve the durability of the belt portion.

[0005]

A tire of the present invention has at least two belt layers made of aromatic polyamide fiber cords or steel cords, and an edge tape is disposed between the ends of the at least two belt layers. As the coated rubber and the edge tape for these belt layers, 1.0 to 5 parts by weight of a partial condensate of hexamethylol melamine pentamethyl ether and 0.5 part of a cresol resin are used for 100 parts by weight of the raw material rubber. .About.5 parts by weight, 4 to 7 parts by weight of sulfur, and 0.1 to 0.8 parts by weight of an organic acid cobalt salt as a cobalt element are used.

As described above, according to the present invention, since the specific rubber composition is used not only for the coat rubber of the belt layer but also for the edge tape, this rubber composition is applicable not only to the steel cord but also to the aramid fiber cord. Since it has excellent adhesiveness and water resistance, it is possible to prevent the occurrence of separation at the end portion of the belt layer and improve the durability of the belt portion.

The structure of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a half-section explanatory view in the meridian direction showing an example of the tire of the present invention. In FIG. 1, a carcass layer 2 is mounted between a pair of left and right bead cores 1, 1, and a tread portion 3 has two belt layers, an inner belt layer 4d and an outer belt layer 4u, on the outer side of the carcass layer 2. It is arranged in a ring shape in the circumferential direction over the entire circumference of the tire.
Aramid fiber cords or steel cords are used for the belt layers 4u and 4d. In the present invention, at least two belt layers are provided, which is a belt layer made of aramid fiber cords or a belt layer made of steel cords.

The end portion of the outer belt layer 4u and the inner belt layer 4
As shown in FIG. 1, the edge tape 5 is annularly arranged between the ends of d in the tire circumferential direction over the entire circumference of the tire. The thickness of this edge tape 5 is 0.6 to 1.5 m.
m, width 15 to 25 mm. The edge tape 5 should just be arrange | positioned between the edge parts of at least 2 layers of belt layers.

In the present invention, a specific rubber composition is used as the coat rubber and the edge tape of these belt layers. This rubber composition comprises 1.0 to 5 parts by weight of a partial condensate of hexamethylolmelamine pentamethyl ether, 0.5 to 5 parts by weight of a cresol resin, and 4 to 7 parts by weight of sulfur per 100 parts by weight of a raw rubber. , And an organic acid cobalt salt as a cobalt element in an amount of 0.1 to 0.8 parts by weight.

(A) Raw rubber. For example, natural rubber (NR), polyisoprene rubber (I
R), polybutadiene rubber (BR), butyl rubber, acrylonitrile / butadiene copolymer rubber (NBR), styrene / butadiene copolymer rubber (SBR), and mixtures thereof. Preferably, natural rubber or polyisoprene rubber containing 50% or more is used as the raw material rubber.

(B) Partial condensate of hexamethylolmelamine pentamethyl ether. The partial condensation product of hexamethylol melamine pentamethyl ether is a compound having the following formula.

[0012] As the partial condensate of hexamethylolmelamine pentamethyl ether, a general commercial product can be used.
For example, Sumikanol 507 (containing 50% of a partial condensate of hexamethylol melamine pentamethyl ether) manufactured by Sumitomo Chemical Co., Ltd. is available. In addition, other polymethoxymethyl melamine,
For example, even if hexamethoxymethylmelamine is used, the object of the present invention cannot be achieved.

The amount of the partial condensate of hexamethylolmelamine pentamethyl ether used is 1.0 to 5 parts by weight based on 100 parts by weight of the raw rubber. If it is less than 1.0 part by weight, the effect of improving the hardness becomes insufficient, while if it exceeds 5 parts by weight, the breaking property is deteriorated. (c) Cresol resin.

A general commercial product may be used. As the cresol resin, a meta-cresol resin is mainly used. The amount used is 0.5 to 5 parts by weight based on 100 parts by weight of the raw rubber. If it is less than 0.5 part by weight, the effect of improving the hardness is small. If it exceeds 5 parts by weight, the breaking property is deteriorated and the exothermic property of the vulcanized rubber is increased, which is not preferable. (d) Sulfur.

The amount of sulfur used is 4 to 7 parts by weight based on 100 parts by weight of the raw rubber. This is because if it is less than 4 parts by weight, the effect of addition is small, and if it exceeds 7 parts by weight, sulfur blooms on the surface of the unvulcanized rubber, which becomes an obstacle in processing. (e) Organic acid cobalt salt. For example, cobalt salts such as cobalt naphthenate, cobalt stearate, cobalt octylate, and cobalt oleate, such as linear or branched monocarboxylic acids having 5 to 20 carbon atoms, boric acid-organic acid cobalt complex (for example, Manchem "Manobond 680C" manufactured by the same company).

The amount of the organic acid cobalt salt used is 0.1 to 0.8 part by weight based on 100 parts by weight of the raw material rubber as the cobalt element. If it is less than 0.1 part by weight, it will be too small,
On the other hand, even if it exceeds 0.8 parts by weight, the improvement of the compounding effect is not observed. (f) The above rubber composition is prepared by blending the above raw rubber with a partial condensate of these hexamethylol melamine pentamethyl ethers, a cresol resin, sulfur, and a cobalt salt of an organic acid. Other compounding agents, such as carbon black and vulcanization accelerator, may be appropriately compounded according to the above.

[0017]

【Example】

Examples 1-2 and Comparative Examples 1-3 Tires having the structure shown in Fig. 1 were produced. In this case, the outer belt layer 4u was made of 1500D / 2 aramid fiber cord, and the inner belt layer 4d was made of steel cord. The cord of the outer belt layer 4u was laminated on the cord of the inner belt layer 4d with a bias. These belt layers 4
As the coated rubber of u, 4d and the edge tape 5,
A rubber composition having the formulation content (parts by weight) shown in Table 1 was used. The tensile strength, elongation at break, and hardness of this rubber composition after vulcanization were measured according to JIS-K-6301.

Then, the following separation resistance drum test was conducted. The results are shown in Table 1. Separation resistance drum test : For the above tires,
Speed on the drum 60km / h, slip angle ± 3 °, camber angle 2 °, load 127% (JATMA standard), air pressure 1.
After traveling at 6000 km at 2 kg / cm ² , the tire was disassembled, the separation amount at the end of the belt layer was measured, and the index was displayed based on Comparative Example 1. The smaller the number, the better.

[0019] As is clear from the results of Table 1, according to the present invention, the strain at the belt interlayer edge portion of the tire is suppressed, and the fracture characteristics are improved, which is effective in preventing separation of the edge portion.

[0020]

According to the present invention, since the belt layer of the tire is composed of the aramid fiber cord and the steel belt cord, and the coat rubber and the rubber tape of both belt layers are the same rubber composition, the belt layers are Since there is no difference in physical properties, it is effective in preventing separation of the end portions of the belt layer, and the uniformity of physical properties of the tire such as modulus is improved. Moreover, this rubber composition not only has excellent adhesion to both steel cords and aramid fiber cords, but also has excellent water-resistant adhesion to aramid fiber cords, so the belt layer on the tire tread surface side That is, it is possible to effectively prevent separation due to moisture absorption when a belt layer made of an aramid fiber cord is used as the outer belt layer, and to greatly improve the durability of the tire belt portion. Further, since the coat rubber and the rubber tape of both belt layers are the same rubber composition, it is not necessary to use two or more kinds of rubber compositions as in the conventional case, so that it is possible to improve tire productivity. Become.

[Brief description of drawings]

FIG. 1 is a half cross-sectional explanatory view in the meridian direction of an example of a tire of the present invention.

[Explanation of symbols]

1 bead core, 2 carcass layer, 3 tread portion, 4d inner belt layer, 4u outer belt layer, 5
Rubber tape.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C08K 5/09 KDB 7167-4J C08L 21/00 LBN 8016-4J // (C08L 21/00 61: 12 8215-4J 61:28) 8215-4J B29K 21:00

Claims (1)

[Claims] 1. A tire having two belt layers composed of aromatic polyamide fiber cords or steel cords, wherein a partial condensate of hexamethylolmelamine pentamethyl ether is added in an amount of 1.0 to 5 with respect to 100 parts by weight of a raw rubber. Parts by weight, cresol resin 0.5 to 5 parts by weight, sulfur 4 to 7
Parts by weight and organic acid cobalt salt as cobalt element
A pneumatic radial tire in which a rubber composition blended with 0.1 to 0.8 parts by weight is used as a coat rubber for the belt layer and is arranged at an end portion of the belt layer.